Keeping your home warm and supplied with hot water is essential, and the right boiler makes all the difference. But how do you choose among the different boiler types? In this complete guide, we’ll explain the three main types of boilers – combi, system, and regular – and help you decide which is best for your home. Whether you’re sorting a boiler repair in North Down or lining up a fresh install, here’s what to know.
Types of Boilers Explained
Modern home boilers generally come in three types: combi boilers, system boilers, and regular (conventional) boilers. Each type works differently and has its own advantages. Here’s an overview:
- Combi Boiler (Combination Boiler) – A combi boiler is an all-in-one unit that provides both heating and hot water on demand. It doesn’t require a separate hot water tank or cold water storage tank. These are compact, efficient and deliver hot water on demand without the need for tanks. Great for smaller homes with limited space. According to the Energy Saving Trust, combi boilers can help cut down on energy waste by only heating what you use.
- System Boiler – A system boiler heats your central heating system directly and also stores hot water in a tank (cylinder) for use. It takes water from the mains supply, so no cold water loft tank is needed, but a hot water cylinder is required.
- Regular Boiler (Conventional or Heat-Only Boiler) – A regular boiler is the traditional setup with a boiler unit plus a separate hot water cylinder and a cold water storage tank (usually in the loft). It’s sometimes called a heat-only boiler and works with older radiator systems.
Each boiler type suits different home sizes and needs. In the sections below, we’ll look at each type in detail, including how they work, their pros and cons, and the kind of home they are best for.
Combi Boilers: Compact and Instant Hot Water
What is a combi boiler? A combi boiler takes care of both your heating and hot water without needing any extra tanks, it just does the job, straight from the mains. When you turn on a hot tap or shower, the combi boiler fires up and instantly heats water from the mains supply. There’s no need for a storage cylinder or a loft tank, which saves a lot of space in your home.
Combi boilers are very popular in the UK for good reasons:
- Instant Hot Water on Demand: You get hot water whenever you need it, without waiting for a tank to heat up. This is convenient for busy households – no more running out of hot water in the middle of a shower.
- Saves Space: All the components are inside one unit, so you don’t need a hot water cylinder or tanks in the loft. This makes a combi ideal for smaller homes or flats where space is tight.
- Energy Efficient: Combi boilers heat only the water you use, exactly when you need it. They don’t keep a tank of water hot when it’s not needed, avoiding wasted energy. Modern combi boilers are condensing boilers with high efficiency (over 90%). In fact, all new combi boilers in the UK must have an energy efficiency rating of at least 92%, which can help lower your gas bills.
System Boilers: Great for Larger Homes with High Demand
What is a system boiler? A system boiler has two main components: the boiler unit (usually wall-mounted, like a combi) and a separate hot water cylinder for storing hot water. Unlike a regular old-style boiler, a system boiler is fed directly from the mains water supply, so you don’t need a cold water tank in the loft. Many of the important components (like the pump and expansion vessel) are built into the boiler unit itself. The system boiler heats water and stores it in the cylinder, ready for use when you need a bath or shower, or to supply multiple taps.
Ideal for Multiple Bathrooms
System boilers can supply hot water to several taps or showers at once without a big drop in pressure. Because hot water is stored in a cylinder, a family can run two showers simultaneously or a shower and a bath, which would be difficult for a combi. If you’ve got more than one bathroom and a few people needing hot water at the same time, a system boiler can make a big difference.
Good Water Pressure
Since a system boiler takes water directly from the mains and heats it, you get hot water at mains pressure from the taps. This often means a stronger, more powerful shower compared to a gravity-fed regular boiler system. If you’ve had issues with weak hot water pressure in the past, a system boiler could be a solution (assuming your mains water pressure is adequate).
No Cold Water Tank Needed
Unlike a traditional regular boiler, a system boiler doesn’t require a separate cold water storage tank in the loft. This frees up space and also removes the worry about tanks freezing in winter or taking up your loft space. For homes without a loft or those planning a loft conversion, a system boiler is much more convenient than a regular boiler.
Compatible with Solar Thermal
Many system boilers can work with solar hot water systems. If you ever plan to use solar panels to heat your water, a system boiler with the right type of hot water cylinder can integrate with that setup. This can be a way to improve efficiency and reduce bills by using renewable energy for water heating.
Regular (Conventional) Boilers: The Traditional Setup
What is a regular boiler? A regular boiler (also known as a conventional, heat-only, or open-vent boiler) is the traditional boiler system that many older homes have. It consists of the boiler unit itself (to heat water), a hot water cylinder (to store hot water), and usually two tanks in the loft, a large cold water storage tank, and a smaller feed and expansion tank. The cold water tank in the loft feeds water to the cylinder and boiler, and gravity creates the water pressure for the system. Regular boilers have been largely superseded by combi and system boilers in new installations, but they are still used in certain situations and many older systems are of this type.
Can Serve Large Homes and Low-Pressure Areas:
Conventional boilers are well suited to homes in areas with low mains water pressure, because the water pressure for hot water comes from the gravity-fed tank in the loft. If your mains pressure is very poor, a regular boiler with a loft tank can still provide decent flow by relying on gravity. They can also handle supplying water to many outlets if the plumbing is designed for it, as was common in large older houses.
Hot Water Backup via Immersion Heater:
With a hot water cylinder, you often have an electric immersion heater inside as a backup. This means if the boiler breaks down, you could still heat water using electricity in the cylinder. It’s not as efficient as the boiler, but it provides a safety net so you’re not completely without hot water in an emergency.
Compatibility with Older Heating Systems:
If your home already has an older heating setup with a regular boiler, it might be more straightforward and cost-effective to replace it with another regular boiler rather than rework everything. Older radiators and pipework that might not handle the higher pressure of a combi or system boiler will work fine with a conventional boiler (since it’s low-pressure). This can avoid the need to upgrade a lot of the existing plumbing in some retrofit cases. In short, if your home has an older pipe system, sticking to a conventional boiler could be less disruptive.
How to Choose the Right Boiler for Your Home
Now that we’ve outlined the main types of boilers, how do you decide which one is right for your home? The choice will depend on several factors:
Home Size and Hot Water Demand
Consider how many bathrooms or showers you have, and how many people live in your home. As mentioned earlier, a combi boiler is usually ideal for a small home or flat with one bathroom and lower hot water demand. If you rarely have simultaneous hot water usage, a combi should suffice. On the other hand, if you have a larger family home with multiple bathrooms, a system boiler is likely more suitable because it can handle higher simultaneous demand. A regular boiler could also serve a large home well, but a system boiler will provide similar multi-outlet service without the need for a loft tank. Essentially, match the boiler to your usage: one bathroom = combi is fine; two or more bathrooms used at once = consider system (or conventional).
Space Availability
Think about where the boiler and its components will go. A combi boiler wins in space-saving – it’s just one wall-hung unit, great for small properties. If you live in a small terrace house or apartment in Bangor, you might not have room for a hot water cylinder or loft tanks, making a combi the obvious choice. System boilers need space for a cylinder (often an airing cupboard). Regular boilers need a cylinder and loft space for tanks. If you have a loft and aren’t worried about space, all options remain open. If not, you’re basically looking at a combi or system (if you have a cupboard for the cylinder). It’s important to be realistic about space – there’s no point getting a system boiler if you have nowhere to put the cylinder.
Mains Water Pressure
Your home’s incoming water pressure can influence your choice. Combi and system boilers rely on decent mains pressure to give good flow at your taps. If the mains pressure is low in your area, a combi might give disappointing shower performance. Regular (conventional) boilers can bypass this by using a loft tank for pressure. You can have a plumber or heating engineer in Bangor check your mains water pressure if you’re unsure. If it’s low, you might lean towards a system with pumped solutions or stick with a conventional setup that uses gravity, or install a booster pump. For most homes on a modern mains supply, this won’t be an issue, but it’s worth checking.
Existing System and Infrastructure
Consider what type of boiler you currently have. Replacing like-for-like can be simpler and cheaper. For instance, swapping an old combi for a new combi is straightforward. But if you currently have a regular boiler with tanks, you could either replace it with a new regular boiler or switch to a system or combi. Switching may involve extra work – e.g., removing old tanks, altering pipework, and possibly upgrading radiators or pipes. A qualified engineer can advise on what upgrades would be needed. If your existing system is old but you want the benefits of a combi, the engineer might need to do things like flush out old pipes or even replace sections to handle mains pressure. The condition of your current system can therefore influence what’s practical.
Will Your Heating System Meet Tomorrow’s Demands?
Are you planning an extension, additional bathroom, or loft conversion? If you expect your hot water demand to increase (say you plan to add another bathroom), it might be wise to choose a system boiler now instead of a combi, to be ready for the extra demand. Conversely, if you are downsizing or using the loft (where tanks are) for living space, you’d want to eliminate the tanks by moving to a combi or system boiler. Also, consider if you want to integrate renewable energy (like solar water heating) – system boilers are more amenable to that integration.
In many cases, homeowners in North Down and Bangor consult with a professional heating engineer to assess these factors. It’s often part of a free quotation visit for a boiler installation in North Down or Bangor that the engineer will check your home, ask about your water usage, and then recommend the best type and size of boiler. This personalised advice is very valuable because every home is a bit different.
Efficiency and Cost Considerations
Modern boilers are all designed to be efficient, but there are a few points to consider regarding energy efficiency and costs:
All New Boilers are Condensing
Since 2005, virtually all new gas boilers installed in the UK are condensing boilers. This means they have a technology that recovers extra heat from the exhaust gases, boosting efficiency. In practice, this gives efficiencies of around 90% or higher for gas boilers of all types (combi, system, or regular). So if you are replacing an old non-condensing boiler (pre-2000s era), any new boiler you choose will likely reduce your gas usage just by being condensing. For example, a new combi boiler will have at least an A-rating (~92% efficiency or more) by law. System and regular boilers also will be high-efficiency models if new.
Combi vs System Efficiency
Between boiler types, combi boilers are often cited as slightly more efficient in day-to-day running because they only heat water on demand and don’t have the standing heat losses of a stored hot water system. If you have low to moderate hot water needs, a combi can be very frugal since it doesn’t heat a full cylinder of water that might not be used. However, if you have high hot water usage (say a big family taking multiple baths and showers), a system boiler might actually be more practical and could even be cheaper to run in some cases. This is because heating water in bulk for heavy use can be efficient, and a combi might end up working hard and still possibly “wasting” some water (for example, you often have to run the tap for a few seconds to get hot water with a combi, which can waste water).
The differences in running cost will depend on your usage pattern. For most average households, all modern boilers are comparably efficient, and usage habits will determine bills more than the type of boiler.
Heat Loss Considerations
If you go with a system or regular boiler, invest in a good insulated hot water cylinder. Modern cylinders have thick insulation (often foam) to keep water hot for hours. This mitigates the efficiency gap between stored hot water systems and combis. Also, insulating the hot water pipes (lagging) helps reduce heat loss. These are usually handled by the installer, but it’s good to be aware.
Installation Costs
The cost of the boiler itself and installation can vary by type. Combi boilers are just one unit to install, and if it’s a straight swap, labor costs are typically lower. System boilers require installing a cylinder and maybe additional controls, which can increase installation time and cost. If switching types (e.g., converting from regular to combi), removal of tanks and old piping adds to labor. In some cases, especially if your current boiler is very old, you might need upgrades like a larger gas supply pipe or new flue, which can affect cost. While we won’t quote exact prices (those vary widely), expect a combi swap to be the most budget-friendly install, with system or conventional installs being a bit more, both for parts (cost of cylinder, etc.) and labour.
Maintenance Costs
All boiler types should be serviced annually to keep them running safely and efficiently. A boiler service in Bangor by Baylands Plumbing and Heating, for example, is a routine check that can catch issues early and keep your boiler in top condition. The cost of a standard service doesn’t differ much by boiler type (though a system or regular boiler has a cylinder which isn’t really “serviced” but may have its own controls to check). Over the long term, combi boilers have more complex parts inside (heat exchangers, diverter valves) whereas system boilers have slightly fewer moving parts in the unit but more external components.
Realistically, all modern boilers are reliable if maintained. Some people opt for maintenance plans or insurance, especially for combi boilers, because a breakdown affects everything (heat and hot water). But a well-installed boiler of any type should last many years with minimal repair costs, aside from the annual service.
Lifespan and Replacement
How long will your boiler last? Typically, a modern boiler will last around 10-15 years with proper maintenance. After that, efficiency may drop and the risk of breakdowns increases. If your boiler is over 15 years old, even if it’s working, it could be worth considering a new one for efficiency and reliability. In terms of type, there isn’t a huge difference in lifespan – it often depends more on the brand, model, and maintenance. Some high-end boilers might last longer, and old cast-iron regular boilers sometimes soldier on for decades (albeit inefficiently). But as a rule of thumb, budget for replacement around the 15-year mark. Keep this in mind when calculating long-term costs: if your boiler is already 12+ years old and you’re facing an expensive repair, it might be more cost-effective to put that money toward a new boiler.
Finding the Right Boiler and Expert Help
Choosing the right boiler type for your home is a balance of your household’s needs, your property, and your budget. Combi boilers are perfect for smaller homes or flats with one bathroom and can save space and energy. System boilers shine in larger homes with multiple bathrooms, providing strong hot water performance at multiple outlets. Regular boilers are the traditional choice for very large or older homes, especially where mains pressure is low or the infrastructure is already in place.
It’s important to have a qualified professional guide you through the decision and carry out the installation. A knowledgeable heating engineer will ensure your new boiler is properly sized, safely installed, and set up for efficient operation. They’ll also handle the old boiler removal and make the process as smooth as possible for you. Remember, a boiler is a significant investment in your home’s comfort – getting it right will pay off in reliable heating and hot water for years to come.
If you’re still unsure which boiler is right for your home, or you’re considering an upgrade, why not reach out for expert advice? Contact Baylands Plumbing and Heating for friendly, professional guidance. We are a local plumbing and heating company serving Bangor and the North Down area with over 15 years of experience. Our Gas Safe registered engineers can help you with everything from routine boiler service in Bangor to emergency boiler repair in North Down, as well as complete boiler installation in North Down and surrounding regions.
About the Author
At Baylands Plumbing and Heating, we bring over 15 years of experience to every job. We’re Gas Safe and Phoenix registered, with a strong track record in both boiler installation and heating system maintenance. Our team has been recognised within the trade, including nominations for national awards. We believe in straightforward, honest advice and take pride in helping homeowners make informed decisions about their heating.